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Re: [Xen-devel] [PATCH RESEND v1 0/7] Intel Processor Trace virtulization enabling

On Tue, Jan 16, 2018 at 02:12:26AM +0800, Luwei Kang wrote:
> Hi All,
> Here is a patch-series which adding Processor Trace enabling in XEN guest. 
> You can get It's software developer manuals from:
> https://software.intel.com/sites/default/files/managed/c5/15/architecture-instruction-set-extensions-programming-reference.pdf

Now Chapter 4.
> Introduction:
> Intel Processor Trace (Intel PT) is an extension of Intel Architecture that 
> captures information about software execution using dedicated hardware 
> facilities that cause only minimal performance perturbation to the software 
> being traced. Details on the Intel PT infrastructure and trace capabilities 
> can be found in the Intel 64 and IA-32 Architectures Software Developer’s 
> Manual, Volume 3C.
> The suite of architecture changes serve to simplify the process of 
> virtualizing Intel PT for use by a guest software. There are two primary 
> elements to this new architecture support for VMX support improvements made 
> for Intel PT.
> 1. Addition of a new guest IA32_RTIT_CTL value field to the VMCS.
>   — This serves to speed and simplify the process of disabling trace on VM 
> exit, and restoring it on VM entry.
> 2. Enabling use of EPT to redirect PT output.
>   — This enables the VMM to elect to virtualize the PT output buffer using 
> EPT. In this mode, the CPU will treat PT output addresses as Guest Physical 
> Addresses (GPAs) and translate them using EPT. This means that Intel PT 
> output reads (of the ToPA table) and writes (of trace output) can cause EPT 
> violations, and other output events.

How does one test this functionality in Linux? As in does 'perf' take advantage 
of the Processor Trace

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